1. Field of the Invention
The invention relates to electrographic recording apparatus and methods wherein an electrographic writer establishes electrical fields that are used to selectively develop toner into an image.
2. Description Relative to the Prior Art
In the art of electrographic recording, it is well known to provide an electrographic writer or writehead that has a series of electrodes that can be selectively activated to selectively deposit charge and thereby record an electrostatic image on an insulative recording member. The electrostatic image is then advanced to a development station wherein the electrostatic image is developed to be visible by selectively attracting visible marking particles such as liquid or dry toner particles to deposit on the insulative recording member. The developed toner image is then transferred and fused to a receiver member such as plain paper or plastic to form a permanent record of the image.
A problem with electrographic recording on an insulative recording member using an ionographic recorder is that it is difficult to control position or placement of a charge pixel on the recording member and thus the recording images are not as well defined as in electrophotographic recording. Electrographic recording is distinguishable from electrophotographic recording in that the image is not required to be formed on a light sensitive member and light is not used in recording the image.
In order to improve upon electrographic recording there has recently been described by Oce Nederland B. V. a direct imaging electrographic writer that features a rotatable cylindrical writehead in the form of a drum. The drum has imbedded ring electrodes that are selectively provided with a voltage to attract toner in a development station. As the writer drum rotates, the voltages on the ring electrodes change in accordance with image data to form a toned image on the writehead. The toned image on the writehead is then transferred to a heated transfer roller and then simultaneously transferred to paper and fused.
A problem associated with development of toner images on the writehead itself is the buildup of contamination on the writehead which affects adversely the quality of the images formed thereon.
It is therefore an object of the invention to provide an improved electrographic apparatus and method that reduces the contamination problem and avoids the problem of having to place the electrostatic image well upstream of the development station and does not require use of an electrophotoconductive member.